In recent years, an iron-type golf club head having large moment of inertia around a vertical axis passing though the center of gravity of the club head has been proposed.
(cf. The Following Patent Document 1)
Such club head is hard to rotate around the vertical axis even if a ball hits at a position off the center of the club face toward the toe or heel, therefore, directionality of the hit ball is improved.
Further, an iron-type golf club head having a lowered center of gravity of the club head has been proposed.
(cf. The Following Patent Document 2 and 3)
Such club head increases a chance to hit a ball at a position on the upper side of the sweet spot of the club face.
If a ball is hit at a position on the upper side of the sweet spot, the club head is rotated by a very small angle so as to increase the loft angle, therefore, the launch angle of the ball becomes increased. Thus, for the iron-type golf club head having a lowered center of gravity of the club head, it is easy to hit a golf ball high in the air. This helps to increase the carry.
Accordingly, an iron-type golf club head having high moment of inertia and a lowered center of gravity can improve the carry and directionality of the hit ball.    [Patent document 1] Japanese Patent Application Publication No. H09-253248    [Patent document 2] Japanese Patent Application Publication No. H10-295861    [Patent document 3] Japanese Patent Application Publication No. 2014-000410